1. Field of the Invention
This invention relates to car washing apparatus having a rotary brush, and more particularly, to apparatus for detecting the position of objects, such as license plates, mounted on the exterior of a car to prevent detachment thereof during a washing operation.
2. Description of Related Prior Art
In car washing installations of the type wherein a car is scrubbed by rotary brush apparatus either urged against a car advancing along a conveyor or advanced along the exterior of a stationary car, there has been known heretofore means to prevent the detachment of a license plate as the brush passes therepast.
For example, car washing installations in Europe accomplish this task by using brush apparatus comprised of a pair of counterrotating brushes stacked on a vertically disposed shaft which provides a common axis of rotation for both brushes. The brushes are positioned at a height so that the point where the two brush ends meet corresponds to the midpoint of the height of the license plate mounted on the car. As the counterrotating brushes travel along the front or rear end of the car and encounter a license plate mounted thereon, they exert on the vertical ends of the license plate forces of approximately equal magnitudes and opposite directions to reduce the tendency of a brush to grab and pull at the ends thereof.
This technique of applying compensating brush rotational forces is practiced in Europe primarily because European license plates, unlike those in the United States, are characterized by long horizontal and short vertical dimensions. License plates of this type, therefore, present short vertically disposed ends which enhance the probability of a sufficient balancing of forces under the counterrotating brush technique.
The counterrotating brush technique for reducing the tendency of rotating brushes to detach a license plate during a scrubbing operation suffers from several disadvantages.
First, counterrotating brushes can effectively protect a license plate mounted on a car at only a standardized height above the ground surface. License plates located at other heights cannot experience the balanced scrubbing forces that constitute the operating principle of the technique. In addition, a license plate of the type found in the United States, even if mounted at the height required under this technique, would experience along its longer vertical dimension a substantially nonuniform distribution of forces exerted by the counterrotating brushes which would introduce a twisting force and thereby tend to bend or detach the license plate.
Second, the mechanism for counterrotating two brushes mounted on a common shaft is necessarily complicated by a requirement for additional and redundant components to drive and control brushes rotating in opposite directions.
Finally, the lengths of the upper and lower brushes are not dictated by considerations such as interchangeability for replacement purposes or optimum positioning for increased scrubbing efficiency, but merely by the anticipated mounting height of the license plates on the cars to be washed.
An important object of this invention, therefore, is to provide means to detect the position of an object, such as a license plate, on the exterior of a car during the washing thereof by slowing the speed of brush rotation upon detection of the location of the brush near the object.
Another important object of this invention is to provide a detection means wherein the brush drive mechanism rotates the individual component brushes in the same direction.
A further important object of this invention is to provide a detection means that is an integral part of the rotary brush drive mechanism, thereby requiring minimal additional drive components.
Still another important object of this invention is to provide a detection means that is effective irrespective of the shape of the object or its location on the car.
Another object of this invention is to provide a detection means that is independent of the configuration or size of the individual component brushes of the rotary brush apparatus.
Another object of this invention is to provide a detection means that is adaptable to different types of conventional rotary brush drive mechanisms, such as electrical and hydraulic mechanisms.
Another object is to provide a detection means suitable for mounting on either passive or mechanized support and guide structures for a rotary brush.